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Treatment of mycotic aneurysm of the abdominal aorta due to Salmonella species with in situ synthetic graft
(Portuguese PDF version)

Edvaldo de Souza¹, Celso Luiz Muhlethaler Chouin², Paulo Eduardo Ocke Reis³, Angel Rafael Borja Cabrera⁴

1. MSc. Specialist in Angiology and Vascular Surgery, Sociedade Brasileira de Angiologia e Cirurgia Vascular - SBACV. Vascular Surgeon, Hospital Universitário Antônio Pedro, Universidade Federal Fluminense (UFF), Rio de Janeiro, RJ.
2. MSc. Vascular Surgeon, Hospital Universitário Antônio Pedro, Universidade Federal Fluminense (UFF), Rio de Janeiro, RJ.
3. Specialist in Vascular Surgery, SBACV. Chairman, Serviço de Cirurgia Vascular, Hospital Universitário Antônio Pedro, Universidade Federal Fluminense (UFF), Rio de Janeiro, RJ.
4. MD, Serviço de Cirurgia Vascular, Hospital Universitário Antônio Pedro, Universidade Federal Fluminense (UFF), Rio de Janeiro, RJ.

Correspondence:
Edvaldo de Souza
Rua Arruda Alvim, 49/122
CEP 05410-020 - São Paulo, SP
Tel.: (11) 3081.0223
E-mail: ed@predialnet.com.br

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ABSTRACT

A case report of mycotic aneurysm of the infra-renal abdominal aorta caused by Salmonella species. Patient presented with abdominal pain, pulsatile mass and fever with one-month clinical evolution. Abdominal computed tomography showed sacular aneurysm of the infra-renal abdominal aorta. The patient was submitted to surgical treatment with resection of the infra-renal aorta, large debridement of compromised tissues, prosthetic graft interposition and long-term antibiotics.

Key-words: infected aneurysm, abdominal aorta, Salmonella, abdominal pain, debridement.
Palavras-chave: aneurisma micótico, aorta abdominal, Salmonella, dor abdominal, desbridamento..

J Vasc Br 2004;3(2):165-8

The term mycotic aneurysm, although imprecise, is well known in the medical literature. Patel & Johnston¹ classified mycotic aneurysms according to a pre-existing condition of the arterial wall (normal, atherosclerotic and aneurysmatic), and to the origin of the infection (intravascular contamination versus extravascular). Mycotic aneurysms are uncommon, representing 3 to 5% of all aneurysms detected at autopsies.^2,3 Salmonella is cited as the germ that causes mycotic aneurysm of the abdominal aorta, accounting for 18 to 35% of cases.^2,4

Salmonella mycotic aneurysms of the aorta had fatal evolution until 1962 when Sower & Whelan⁵ reported a case of a patient treated by surgical excision and in situ graft for revascularization. The two major methods to treat a mycotic aneurysm of the abdominal aorta are the revascularization with in situ graft (interposition of the prosthesis in continuity with the normal vessel at the infected arterial bed) after en bloc resection of the compromised aorta and debridement of the infected tissue; and the extra-anatomic revascularization after ligation of the abdominal aorta and debridement of the infected tissue. A consensus about the best treatment has not yet been reached.^2-4,6-8

The authors report a case of mycotic aneurysm of the infra-renal abdominal aorta due to Salmonella species. The patient was treated with in situ Dacron graft, following en bloc resection of the compromised aorta and debridement of the infected tissue.

CASE REPORT

A.H.C., a 65 year-old black male from Rio de Janeiro, was admitted at the emergency room of Hospital Antônio Pedro on September 10, 2003. The patient presented with abdominal pain, fever (38 °C) and 30 days of weight loss evolution. One day prior to admission, the patient underwent ultrasonography that revealed aneurysmal dilatation of the infra-renal abdominal aorta with irregular shape and variable diameters 4.4 x 3.4 x 3.7 cm.

On physical examination, a firm, tender pulsatile mass, measuring around 4 cm, was found, located in the mesogastric region. Hemogram results revealed Hb = 15 g/dl, Ht = 44,5%, white blood cell count = 11.400/ul, and platelet = 319.000/ul.

Abdominal computerized tomography (CT) revealed a sacular aneurysm of the infra-renal abdominal aorta with the larger diameter measuring 4.7 cm, and stretched bladder with increased prostate volume (Figure 1).

Figure 1 - Abdominal CT revealing aneurysm of the infra-renal abdominal aorta and stretched bladder due to prostatic hypertrophy.

On September 12, 2003, with diagnostic hypothesis of mycotic aneurysm, the patient was started on intravenous antibiotics (ceftriaxone 2 g/day + clyndamicin 2.4 g/day) and underwent emergency surgery.

During transoperative period, an aneurysm of the anterior infra-renal abdominal aorta was found. It presented a purple color, with an inflammatory process that stretched mostly to the left side of the aorta bifurcation. Clamping of the infra-renal aorta and common iliac arteries was performed. A small fragment of the aorta was sent to bacterioscopic examination and revealed Gram-negative bacteria. Culture detected Salmonella species growth. The affected aorta was resected and the purple material adhered to the adjacent parts was debrided. Irrigation of the surgical site was performed with physiological saline and a 19 x 8 mm bifurcated Dacron graft was applied.

The postoperative course was satisfactory and the patient was released from the intensive care on the fifth day. On the sixth postoperative day, laboratorial exams were normal. The patient was discharged after eleven days with a prescription for ciprofloxacin 1 g/day for 2 months and clopidogrel 75 mg/day and referral to regular outpatient consultation. Histopathologic finding of the resected aorta was compatible with atherosclerotic disease. Postoperative trans-thoracic echocardiography did not reveal intracavitary or valvar injuries.

DISCUSSION

The term "mycotic aneurysm" became known in 1885 when it was coined by Sir William Osler to describe a case of infectious aneurysm of the aorta of embolic origin associated with bacterial endocarditis.⁹ The spontaneous aortic infection was first recognized in the late 20th century, although Ambrose Pare had already diagnosed aortic syphilitic aneurysm long before, in the 17th century. Since then, several classifications for arterial infections have been published, but the term mycotic aneurysm is still used these days.^3,4,6,10 Before the advent of antibiotics, 86% of arterial infections had bacterial endocarditis as their origin. With the beginning of the antimicrobial therapy, there was a decreased of the incidence of endocarditis and a consequent change of the aortic infection pattern.^3,4,6,11 Nowadays, the direct infection of the aorta with formation of pseudo-aneurysm or infection of a pre-existing atherosclerotic aneurysm is more prevalent and it is the most frequent mechanism of mycotic aneurysm formation.^3,4,6,10 However, only in few cases it is possible to establish the origin of the infection.^3,4

Salmonellosis of the abdominal aorta is little prevalent, but it presents a mortality rate of 50%. Among patients who develop this disease, 25% are over 50 years of age, with predominance of males and higher tropism for atherosclerotic lesion.^2,4

Salmonella is a Gram-negative bacteria and some serotypes present high virulence and are more prone to bacteremia. Patients with chronic diseases are more susceptible to distant infections.^2-4,6,10

About 50% of patients with mycotic aneurysm of the abdominal aorta may present with the clinical triad of fever, abdominal or back pain, and abdominal pulsatile mass.^2-4,6,10-12 Ultrasonography is a high-efficiency noninvasive exam for the initial investigation.^2-4,6,12 Abdominal CT is more sensitive and accurate for establishing diagnosis.^2-4,6,11,12 Arteriography offers some aid in the surgical planning when the visceral aortic branches are involved.^3-4,6,10,11

Long-term antibiotic therapy should be initiated with administration of intravenous antibiotics. Bactericidal action antibiotics, like those derived from penicillin, aminoglycoside, or quinolones, have proved to be more effective agents.^{2,3,7,11,13-15} Concerning surgical treatment, the literature defends resection of the compromised aorta and debridement of the affected tissue, but there is no consensus about the ideal method for revascularization.^2-4,6-8 Nowadays, two types of vascular reconstruction are recommended: in situ graft and extra-anatomic graft.

The satisfactory results obtained with in situ graft for treatment of mycotic aneurysm of the abdominal aorta associated with the use of long term antibiotics suggest re-evaluation of the extra-anatomic graft, since this procedure is not free of complications.^{2-4,6-8,10-12} Reconstruction in situ of the mycotic aneurysm caused by Salmonella may result in a prolonged survival as showed by treated cases when the visceral branches are compromised. ^3,6-8,11,12

Reviews of the literature show that the survival of patients diagnosed with mycotic aneurysm has increased over the years with a success rate of extra-anatomic graft and in situ graft of 64 and 55%, respectively. Mortality rate for patients who underwent in situ graft and extra-anatomic graft is 32 and 36%, respectively.^2,3,6-8,12

At first sight, the interposition of the graft seems to be a suitable choice to treat infected aneurysm, but we should take into account the consequences of infection in the prosthesis that may reach up to 20%. Nevertheless, a prospective study is required in order to prove which procedure is the best choice, unfortunately, this is not viable since there are only few cases in the literature.^{2-4,6,8,11,12,16}

Other alternatives for mycotic aneurysm treatment have also been described: the use of homologous graft, autologous superficial femoral vein, and endoprostheis.^16-20 The basic principle for a successful treatment of mycotic aneurysm include early diagnosis, adequate antibiotic treatment, aorta resection and revascularization with in situ graft or extra-anatomic graft, and long-term postoperative follow-up. ^{2-4,6,7,10-13}

In the present case, the patient presented with the clinical triad of abdominal pain, pulsatile mass and fever. This triad is found in more than 50% of patients with mycotic aneurysm.^2-4,6,10-12 The patient underwent en bloc resection of the infected aorta, debridement of the tissues involved and anatomic revascularization with synthetic graft, which is also considered an alternative for surgical treatment, according to the literature review.^{2-4,6-8,10-13}

Culture identified the presence of Salmonella species that was sensitive to the antibiotics prescribed. This fact caused concern from the beginning of the treatment, since it was verified in previous works that this type bacteria is related to prognosis, evolution and the type of postoperative follow up.^{2-4,6-8,10-12} The hypothesis for the infectious source indicated urinary tract, although there was no previous culture and the patient presented disposition for bladder obstruction. In this case, clinical examination, ultrasonography and abdominal CT did no reveal any other source of infection, seeing that the gastrointestinal tract has been reported as the most common infectious source.^2-4,6,10-12 Trans-thoracic echocardiography excluded the cardiological origin of the infection, which may occur in cases of bacterial endocarditis.^2-4,6,10,11

The patient had satisfactory postoperative evolution, absence of fever and regularization of white blood cell count. He was discharged with a prescription for ciprofloxacine for 60 days and regular outpatient follow-up, seeing that the literature reports cases of medium and long-term complications, regardless the type of operative technique employed.^{2-4,6,7,10-12}

COMMENTS

Early diagnosis of mycotic aneurysm due to Salmonella favors revascularization with in situ graft after a thorough debridement. Long-tem antibiotic therapy is also necessary. However, the results obtained suggest that the conduct adopted in this case was adequate, although the long-term postoperative follow-up is necessary in order to detect possible late complications.

REFERENCES

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14. Lima DR. Doenças infecciosas e parasitárias. In: Lima DR. Terapêutica Clínica. Rio de Janeiro: Guanabara Koogan; 2001. p. 82.

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16. Noel AA, Gloviczki P, Cherry KJ, et al. Abdominal aortic reconstruction in infected fields: early results of the United States cryopreserved aortic allograft registry. J Vasc Surg 2002;35:847-52.

17. Thrush S, Watts A, Fraser SC, Edmondson RA. Primary autologous superficial femoral vein reconstruction of an emergency, infected, ruptured aortic aneurysm. Eur J Vasc Endovasc Surg 2001;22:557-8.

18. Lesèche G, Castier Y, Petit MD, et al. Long-term results of cryopreserved arterial allograft reconstruction in infected prosthetic grafts and mycotic aneurysms of the abdominal aorta. J Vasc Surg 2001;34:616-22.

19. Semba CP, Sakai T, Slonim SM, et al. Mycotic aneurysms of the thoracic aorta: repair with use of endovascular stent-grafts. J Vasc Interv Radiol 1998;9:33-40.

20. Franke S, Voit R. The superficial femoral veins as arterial substitute in infections of the aortoiliac region. Ann Vasc Surg 1997;11:406-12.